Ulster could be without captain Johann Muller for their back-to-back Heineken Cup clashes with Northampton in December after the lock was ruled out for eight weeks.

Muller ruptured ligaments around his thumb during Ulster's 19-8 win over Glasgow Warriors on Friday. Muller was turning out in his 50th appearance for the province and has been a key component in their unbeaten start to the season with them five from five in the RaboDirect PRO12 and two from two in the Heineken Cup.

The second-row underwent the surgeon's knife on Sunday and the club have said he will be out for eight weeks. With Ulster facing Northampton on December 7 and then again eight days later, Muller faces a race against time to prove his fitness by then.

Ulster's next match is away to the Dragons on Friday with Chris Henry expected to take on the captain's armband for that match.